“I was on the dance floor when a large group of people came running in, not in wedding attire,” a friend of the couple, Amy Prada, told HuffPost. “I thought maybe it was a dance mob or something. Then behind all of them, I saw Katy Perry and she went straight to the dance floor with her dance crew. I was shocked!”

Photographer Ray Prop told HuffPost in an email that Perry introduced herself to the couple and said, “Do you mind if we crash your wedding?”

They, of course, were happy to oblige.

Perry was happy to take photos with guests. (Ray Prop Photography)

She danced up a storm. (Ray Prop Photography)

Prada told HuffPost that Perry was “very friendly” and took lots of photos with guests.

Perry and her crew stayed about 15 minutes, according to the photographer.

“Katy congratulated the bride and groom one last time. Then, just as quickly as they had appeared, Katy and her crew were gone,” Prop said.

The pop star even shared some of the wedding fun on her Snapchat stories:

(Katy Perry/Snapchat)

(Katy Perry/Snapchat)

Perry and her crew were in St. Louis for a concert at the Scottrade Center on Sunday, as part of her Witness tour.

And Katy: You can crash our party anytime.

HuffPost also reached out to the bride for comment but had not heard back at the time of publication. This story may be updated.